A mobile communication system needs to be designed in such a way that communication parameters (e.g., such as a spread code, frequency, time slot, neighboring cell list, and transmission power) do not overlap between macro-cell radio base stations, of which their respective macro cells adjacent to each other.
To achieve this, a mobile telecommunications carrier has estimated an area that radio waves from each macro-cell radio base station can reach by conducting a simulation taking into consideration an installation location and a configuration (antenna configuration) of each of the radio base stations, thereby setting communication parameters in each macro-cell radio base station.
When installing a new macro-cell radio base station for the increase in traffic thereafter, the mobile telecommunications carrier needs to set again the communication parameters in each macro-cell radio base station.
Such a method for setting the communication parameters is based on the result of the estimation of the area that the radio waves of each macro-cell radio base station can reach by the simulation. For this reason, when errors actually occur in the result of the estimation of the area that the radio waves of each macro-cell radio base station can reach, the communication parameters sometimes overlap between the radio base stations under which respective macro cells adjacent to each other, and that will bring interference.
In recent years, studies have been made for operational methods of a so-called femto-cell radio base station (Home eNB) which is a radio base station installed in a small area such as a home.
The number of the femto-cell radio base stations to be installed is expected to increase much more than the number of the macro-cell radio base stations installed. The increase of the femto-cell radio base stations leads to an increase in workload required for the method for setting the communication parameters.
As a method for reducing the workload required for the method for setting the communication parameters, there has been proposed a method as follows. In the method, a radio base station in a W-CDMA mobile communication system receives and demodulates a downlink radio signal transmitted by a neighboring radio base station, thereby determining a downlink scrambling code already used by the neighboring radio base station. Then, a downlink scrambling code to be used by the radio base station is automatically determined based on the result of the determination.